Nano-fibrous hydroxyapatite/chitosan (HA/CS) composites with HA contents of 070 wt % were prepared by in situ hybridization with a preprepared chitosan film as semipermeable membrane to slow down the hybridization process. The phase composition, microstructure, and morphology of the composites were characterized by means of Fourier transform infrared spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy. It was found that the in situ prepared inorganic phase was hydroxyapatite nano-fibers that were uniformly dispersed in the chitosan matrix. The average diameter of the fibers were about 3 nm, while the length of the fibers increases from 20 to 60 nm when the hydroxyapatite content increased from 10 to 70 wt %. The compressive strength and Young's modulus of these nano-fibrous HA/CS composites increased with the increasing HA content and reached the highest values of 170 and 1.7 GPa, respectively, at the HA content of 5070 wt %, which were much higher than the values of samples prepared by coprecipitation. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012